What are the steps to assess aortic stenosis with Transthoracic Echocardiography (TTE), according to American Society of Echocardiography (ASE) guidelines?

From the Guidelines

To assess aortic stenosis with transthoracic echocardiography (TTE) according to ASE guidelines, first obtain multiple imaging views including parasternal long-axis, short-axis, apical 3-chamber, 5-chamber, and suprasternal views to evaluate valve morphology and calcification, as recommended by the 2021 ACC/AHA guideline for the management of patients with valvular heart disease 1.

Steps to Assess Aortic Stenosis with TTE

• Obtain multiple imaging views to evaluate valve morphology and calcification
• Measure the left ventricular outflow tract (LVOT) diameter in the parasternal long-axis view in mid-systole
• Use continuous wave Doppler aligned parallel to flow to measure peak aortic jet velocity from multiple windows (apical, right parasternal, suprasternal), recording the highest velocity
• Calculate mean pressure gradient from the velocity curve tracing
• Determine aortic valve area using the continuity equation (AVA = LVOT area × LVOT VTI / AV VTI), where VTI is the velocity time integral measured by pulsed wave Doppler at the LVOT and continuous wave Doppler across the valve
• Assess for pressure recovery in small aortas by measuring the sinotubular junction diameter
• Classify stenosis severity as mild (peak velocity 2.0-2.9 m/s, mean gradient <20 mmHg, AVA >1.5 cm²), moderate (peak velocity 3.0-3.9 m/s, mean gradient 20-39 mmHg, AVA 1.0-1.5 cm²), or severe (peak velocity ≥4.0 m/s, mean gradient ≥40 mmHg, AVA <1.0 cm²)

Additional Considerations

• In low-flow states, dobutamine stress echocardiography may be necessary to distinguish true severe from pseudo-severe stenosis, as noted in the 2021 ACC/AHA guideline 1
• The degree of aortic valve calcification is a strong predictor of clinical outcome, even when evaluated qualitatively by echocardiography, as discussed in the 2021 ACC/AHA guideline 1
• The outflow tract–to–aortic velocity ratio is independent of body size and eliminates potential errors in calculated valve area related to measurement of LV outflow tract diameter or area, as mentioned in the 2021 ACC/AHA guideline 1

From the Research

Assessment of Aortic Stenosis with TTE

According to the ASE guidelines, the following steps can be taken to assess aortic stenosis with TTE:

• Perform a comprehensive physical examination to identify patients with a systolic ejection murmur (SEM) 2
• Use focused cardiac ultrasound (FoCUS) to determine whether patients with a SEM should be referred for standard echocardiography 2
• Assess the aortic valve area (AVA) using the continuity equation and dimensionless index (DI) 3
• Measure the peak jet velocity and mean gradient across the aortic valve 3, 4
• Use nonapical imaging windows, such as the right parasternal window, to determine the severity of aortic stenosis, as the highest peak jet velocity may not always be obtained from the apical window 4

Key Parameters to Assess

• Aortic valve area (AVA) 3, 5
• Peak jet velocity 3, 4
• Mean gradient across the aortic valve 3, 4
• Dimensionless index (DI) 3
• Left ventricular-aortic root angle 4

Importance of Nonapical Imaging Windows

• Neglecting nonapical imaging windows can underestimate the severity of aortic stenosis in up to 23% of patients 4
• The right parasternal window is the most common nonapical window used to obtain the highest peak jet velocity 4